By Gegal Machine Tool
Whether you are an engineer developing a new prototype or a maintenance manager sourcing a replacement component, the question is always the same: What material should this part be made from?
The success of your project depends on this decision. Selecting the wrong material can lead to premature wear, mechanical failure, or unnecessary expenses.
Since 1989, Gegal Machine Tools has guided Mississauga’s manufacturing sector through this exact challenge. With over 32 years of machining experience and facilities in Canada and India, we have learned that the “strongest” material is rarely the correct choice—the right fit is what matters.
This guide provides a framework for selecting between metals and plastics for your CNC machined custom parts.
Part 1: The Fundamental Question – Metal or Plastic?
Before looking at specific alloys or polymers, you must decide on the family of materials. Both metals and engineering plastics offer distinct advantages, but they serve different purposes .
When to choose metal
Metals are the backbone of structural integrity. You should lean toward a metal like aluminum or steel when your part requires high load-bearing capacity, extreme temperature resistance (often exceeding 200°C), or specific electrical conductivity .
Metal parts feel rigid and provide the “heavy-duty” reliability required for industrial machinery, automotive components, and aerospace fittings. They are ideal for high-stress environments like the industrial zones around Mississauga’s Pearson Airport.
When to choose plastic
Modern engineering plastics (like PEEK, Nylon, or Acetal) are not the cheap alternatives of the past; they are high-performance solutions. Choose plastic when weight reduction is critical, when the part must operate silently, or when you need inherent chemical resistance.
Plastics are also naturally insulating. If your part is for a food processing line or medical device, a polymer will often outlast metal by resisting corrosion from cleaning agents .
Part 2: Metals – Strength, Machinability, and Use Cases
At Gegal Machine Tools, we frequently machine a variety of metals for clients across Mississauga. Understanding the nuances below prevents over-engineering (and overpaying) for your parts.
1. Aluminum (The Versatile Performer)
If you are unsure where to start, Aluminum 6061 is often the safe bet. It offers a fantastic strength-to-weight ratio. Because it is soft relative to steel, it allows for high-speed machining, which keeps production costs lower.
- Best for: Electronic housings, drone components, automation arms, and brackets.
- Key trait: Excellent corrosion resistance without needing paint .
2. Steel (The Workhorse)
When durability trumps weight savings, steel is the answer. However, “steel” is a broad category. For custom parts, Stainless Steel (304/316) is popular for its rust resistance, while Mild Steel offers maximum affordability for internal structural parts.
- Best for: Gears, shafts, heavy-duty fixtures, and high-wear industrial tools.
- The Trade-off: Steel requires significant tool pressure. While Gegal’s CNC lathes handle this easily, clients should anticipate a higher cost per part compared to aluminum due to slower machining times and tool wear .
3. Brass (The Precision Choice)
Brass is exceptionally easy to machine (machinability rating of 150% vs. steel’s 100%). It creates smooth, polished finishes right off the machine and offers natural corrosion resistance.
- Best for: Hydraulic fittings, valve components, decorative hardware, and electrical terminals.
- Key trait: It is softer than steel, so it is not suitable for high-impact gears, but it excels in low-friction applications .
4. Titanium (High-Performance)
We rarely recommend titanium unless the physics of the project demands it. It is incredibly strong, light, and biocompatible, but it is difficult to machine and expensive.
- Best for: Medical implants (surgical), racing drones, or aerospace brackets where every gram matters.
- Verdict: Only select Titanium if your operating environment is extreme (high heat, high corrosion, high stress) .
Summary for Metal Selection:
- Low Cost + Lightweight: Aluminum
- High Strength + High Wear: Steel
- Low Friction + Precision: Brass
- Extreme Environments: Titanium
Part 3: Plastics – Beyond the “Plastic” Label
Many manufacturers avoid plastics because they remember brittle, cheap materials. However, industrial-grade polymers machined by Gegal Machine Tools offer properties that metals cannot match.
1. Acetal (POM / Delrin)
Acetal is the machinist’s favorite plastic. It cuts almost like brass, holds incredibly tight tolerances, and has a slippery surface.
- Best for: Gears, bushings, plumbing seals, and food-safe guides.
- Advantage: Unlike metal, it does not require lubrication, making it perfect for moving parts in clean environments .
2. Nylon (PA)
Nylon is tough and absorbs vibrations. It is quieter than metal and resistant to abrasion.
- Best for: Wear pads, conveyor components, and lock nuts.
- Caution: Nylon absorbs moisture from the air, which can cause slight dimensional changes if the part is used in very humid settings .
3. PEEK (The Metal Replacement)
PEEK is a high-performance polymer that can actually replace aluminum or steel in specific scenarios. It is lightweight, incredibly strong, and resists chemicals and heat up to 260°C.
- Best for: Automotive under-hood components, medical devices (sterilization), and electrical connectors.
- The Catch: PEEK material costs are high (approaching cheap metals), but the machining time is lower .
4. ABS
ABS is the standard for rugged prototypes and end-use parts that won’t see extreme stress.
- Best for: housings, dashboards, and low-volume production runs.
- Key trait: It is affordable and easy to finish or paint.
Summary for Plastic Selection:
- Need Precision moving parts? → Acetal (Delrin)
- Need Impact resistance? → Nylon
- Need High Heat resistance? → PEEK
- Need a Cheap Prototype? → ABS
Part 4: The 3-Step Selection Framework
At Gegal Machine Tools, we guide clients through three specific questions to resolve the metal vs. plastic debate.
Step 1: Analyze the Environment
Where will this custom part live?
- Outdoors in Mississauga weather? Avoid standard steel (it rusts). Choose Stainless Steel or Aluminum.
- Submerged in oil or chemicals? Avoid standard plastics (they may swell). Choose Nylon or PTFE.
- Cleanroom / Medical? Often, the choice is Plastic to avoid corrosion and weight .
Step 2: Calculate the “Real” Cost
Do not just look at the raw material price.
- A Titanium part might cost $500 in material and take 4 hours to machine.
- An Acetal part might cost $50 in material and take 1 hour to machine.
- The Question: Does the Titanium part need to last 50 years, or will the Acetal part last 5 years at a fraction of the price? For many non-consumer industrial applications, plastic wins the value test .
Step 3: Mirror the Manufacturing Process
The complexity of the geometry matters.
- Do you need undercuts or very thin walls? Metal may be too rigid and cause chatter; plastic is easier to shape.
- Do you need a mirror finish? Metals (like Brass or Aluminum) polish beautifully. Plastics like Acetal come out with a matte-satin finish right off the CNC.
Part 5: Why Material Expertise Matters in Mississauga
Mississauga is a hub for advanced manufacturing, logistics, and aerospace. At Gegal Machine Tools, we see the consequences of poor material selection regularly.
We recently worked with a logistics client in the Meadowvale Industrial Area who needed a replacement part for a packaging line. Their previous vendor had used standard steel, which was rusting due to the humidity of the cleaning cycle. We remanufactured the part using Nylon 66.
The result?
- The part was 70% lighter, reducing wear on the motor.
- It never rusted.
- It ran silently without lubrication.
This is the advantage of partnering with a machine shop that understands both CNC metals and plastics .
Conclusion: No “Best” Material, Only the “Right” Material
There is no universal answer for custom parts. However, by balancing the mechanical needs (load, heat, friction) with the environmental factors (chemicals, moisture) and the budget volume, you can reach a clear conclusion.
To summarize:
- Structural & Heavy Loads: Go with Steel or Aluminum.
- Lightweight & Chemical Resistance: Go with Nylon or PEEK.
- High Precision & Low Friction: Acetal (Plastic) or Brass (Metal).
Ready to build your custom part?
With facilities in Mississauga (L5T 1M5) and India, Gegal Machine Tools provides CNC milling and turning services for both metal and plastic components. Whether you need a single prototype or a production run, our engineers ensure your material choice aligns perfectly with your application
